Redundancies are sometimes provided in electrical systems to increase safety. This is especially true with respect to areas at risk of explosions, wherein dangerous operating situations should be avoided as much as possible.
With respect to the risk of explosions, dangerous conditions can occur when electrical currents and/or voltages that can generate an ignition spark appear on the lines leading into a dangerous zone. In addition, at appropriate power levels, there is also the risk that components can reach surface temperatures that can ignite an ignitable mixture. Both risks are increasing due to the increase in electrical loads, e.g., modern bus systems, that draw large levels of current.
With this in mind, attention is placed on the power-supply devices and arrangements, so as to guarantee that, in addition to normally provided controls, there are mechanisms in place to rule out dangerous conditions even when an error occurs in the standard control loops.
From the prior art, power-supply devices are known which operate according to the principle of a blocking-oscillator-type converter principle or a feed forward converter. These circuits use transformers with windings featuring galvanic separation and are used to increase or decrease the output voltage relative to the input voltage. These converter circuits contain reaction-coupling mechanisms in order to control the current and/or voltage on the secondary side.
The converter circuits contain, on the primary side, at least one controlled semiconductor switch in series with the primary winding of the transformer, in order to generate the corresponding alternating current. Furthermore, such circuits require a third winding on the transformer, in order to generate the reaction coupling. In the case of printed-circuit transformers, this is inexpedient.